Hernia prosthesis

ABSTRACT

Prosthesis is provided for repairing or resisting the formation of bodily hernia in particular, for inguinal hernia repair or femoral hernia repair. The prosthesis comprises an inner surface and an outer surface, the inner surface forms at least one channel that is sized to receive an anatomical structure and allow it to pass through the prosthesis without substantial compression of the anatomical structure.

FIELD OF THE INVENTION

The present invention relates to prostheses for repairing or resistingthe formation of bodily hernia in particular, but not exclusively, foringuinal hernia repair or femoral hernia repair and a method of usingsaid prostheses.

DISCUSSION OF THE PRIOR ART

A hernia is due to an abnormal protrusion of an organ or part thereofthrough its containing structure, due to a rupture or weakening in alayer of fascia creating an aperture or a defect in the fascia whichcauses it to be less able to contain the organ or part thereof. Herniacan occur at various anatomical positions in the abdomen where there isa weakness in the muscle, and are classified according to the site inwhich they occur.

Two particular types of hernia are inguinal hernia and femoral hernia.

Inguinal hernia occur in the groin when a portion of bladder, bowel ormembrane pushes through a weak spot in the abdominal musculature aroundor at the inguinal canal. The inguinal canal is an opening betweenlayers of abdominal muscle near the groin through which the spermaticcord passes in the male. Typically, inguinal hernia is a male condition.

Two particular types of inguinal hernia occur, direct inguinal herniaand indirect inguinal hernia.

An indirect inguinal hernia passes through the internal ring of theinguinal canal, along the canal and, if the hernia is large enough,emerges through the external ring and in the male descends into thescrotum.

A direct inguinal hernia differs from an indirect inguinal hernia as itpushes its way directly forwards through the posterior wall of theinguinal canal. Occasionally, in unusual circumstances, a direct herniabecomes large enough to push its way through the external ring and theninto the neck of the scrotum.

The femoral artery and vein enter the femoral triangle from beneath theinguinal ligament within a fascial tube termed the femoral sheath. Thefemoral canal is a small, almost vertically-placed gap in the medialpart of the femoral sheath. The function of the femoral canal is tofirstly act as a dead space for expansion of the distended femoral veinand secondly as a lymphatic pathway from the lower limb to the externaliliac nodes.

The femoral canal is a potential point of weakness in the abdominal wallwhich may develop a femoral hernia. The canal is around 1 to 1.5 cm inlength. As the female pelvis is of greater width than the male pelvis,the femoral canal can be somewhat larger in females and female femoralhernia are more common. A femoral hernia is a protrusion through thefemoral canal. The hernia sac may extend through the femoral canal.

Hernia repair generally requires the contents of the hernia to be easedback into position and then for the weakened area to be repaired. Repaircan be effected by tension or tension-free suturing of the tissue andmuscle to strengthen the weakened area or occlude ruptured areas.Alternatively, the weakened or ruptured area can be reinforced using aportion of synthetic mesh.

Meshes for use in the treatment of an inguinal or femoral herniatypically consist of a flat portion of mesh for application over thehernia area. The mesh allows a tension free repair to be made of theweakened area. Such flat meshes have been provided with an aperturetherein or may be cut by a surgeon to allow the mesh to be arrangedaround an anatomical structure which passes through the opening ordefect in the tissue, muscle or organ wall requiring repair or support.

Alternatively, for a well circumscribed defect, e.g. a deep inguinalhernia or femoral hernia, the repair device may be an implantableprosthesis which stops the rupture hole of the hernia.

Implantable prostheses of the prior art include the Bard PERFIX plug™,Ethicon's Prolene Hernia System™, and Surgipro Hernia Mate plug andPatch™ or Atrium Self-forming plugs™.

The Bard PERFIX plug™ is one of the most popular plugs and comprises asurgical mesh fabric arranged to form around 8 leaves or petals, whichare joined in a central region to create a multi-layered cone. Thecentral portion of the plug is pushed into the defect and the leavestrimmed according to the size of the defect such that they stop thedefect. As the leaves project from the central portion, these aid theretention of the plug in the defect. In addition, an overlay patch maybe positioned over the plug which surrounds those tissues surroundingthe inguinal canal. Surgipro Hernia Mate plug and Patch™ and AtriumSelf-forming plugs™ also comprise several leaves and an overlay patchand work in a similar fashion to the Bard product.

Ethicon's Prolene Hernia System™ comprises a first overlay patch forplacing around the inner ring of the inguinal canal, a central portionand a second overlay patch for placing around the outer ring of theinguinal canal. The central portion corresponds to both a portion of thefirst and second overlay patches such that it is held in the inguinalcanal by the two patches to block the canal.

In use, the implantable prostheses of the prior art block the inguinalcanal and prevent a hernia sac from protruding through the canal. Thedefects blocked most effectively by the prostheses are substantiallycircular in cross section, as multi-layer prostheses are inherentlystiff and may not fully conform to variations in the defect. In somecircumstances, when a prosthesis is in use, gaps may be potentially leftbetween the prosthesis and the surrounding tissue, muscle or organ wallof the opening or defect.

This potential for gaps can be increased by anatomical structures whichunder normal circumstances pass through the inguinal canal, such as thespermatic cord, and protrude at the edge of the prosthesis and thiscauses difficulty in completely occluding the defect.

To improve the flexibility of conventional prostheses and thus minimisethe potential gaps between the prostheses and surrounding tissues, someprostheses include pleats moulded into the body of the prostheses.Although, such pleats may to some extent accommodate anatomicalstructures which pass through the defect in the tissue, as such aprosthesis relies on a push fit of the prosthesis into the defect andradial expansion of the leaves of the prosthesis against the tissuessurrounding the defect to hold the implant in place, such a prosthesiswill compress anatomical structures between the prosthesis and thesurrounding tissue. This compression can result in a significantpressure being experienced by an anatomical structure.

Significant pressure is a pressure which causes distortion, compressionor full or partial collapse of an anatomical structure. For example, inparticular examples where a conventional prosthesis is used to treatinguinal hernia, the spermatic cord is squeezed between the prosthesisand the tissues surrounding the aperture and this squeezing may causepain or even damage to the spermatic cord. This can lead to discomfortfor the patient and might lead to long term damage to the structure(s)being compressed and may cause ischaemia of a distal organ. For example,where the anatomical structure includes the spermatic cord, ischaemia ofthe testes may occur as a result of compression of the artery and/orvein along with the spermatic cord.

According to the present invention there is provided a prosthesis forrepair or to resist the formation of hernia of the abdominal wall, theprosthesis comprising at least an outer surface and an inner surfacewherein, the inner surface forms at least one channel through which, inuse, an anatomical structure may pass when the prosthesis is in place inthe body without substantial compression of said anatomical structure.

The channel may be an indentation in the outer surface of theprosthesis.

Preferably the channel is formed along the outer surface of theprosthesis.

An advantage of a prosthesis of the present invention is that byproviding such a channel in the prosthesis, pressure on an anatomicalstructure passing through the channel can be minimised. A reduction orcomplete removal of the pressure on an anatomical structure shouldminimise damage and/or discomfort caused by compression of anatomicalstructures passing through the defect being repaired and minimise therupture or protrusion of a hernia sac through the defect.

In a preferred embodiment of the prosthesis the inner surface defines ascalloped channel.

A scalloped channel is formed by the intersection or indentation of acylinder with the outer surface of the prosthesis.

In a particularly preferred embodiment of the prosthesis the channel hasa substantially semi-circular edge in cross section, such that the innersurface is substantially curved as it interfaces with the anatomicalstructure which the channel receives.

Preferably, in use, the prosthesis is always wholly contained within theextra peritoneal compartment of the abdominal wall.

Preferably the prosthesis is suitable for use in the treatment ofabdominal hernia. More preferably the prosthesis is suitable fortreatment of inguinal or femoral hernia.

In an embodiment of the prosthesis, the prosthesis is provided forrepairing or resisting the formation of an inguinal hernia, the channelbeing sized to accommodate a spermatic cord without substantialcompression of the spermatic cord.

In a preferred embodiment of the prosthesis, wherein the prosthesis isfor use in repairing or resisting the formation of an inguinal hernia,the prosthesis has a longitudinal length or depth in the range 1 cm to 5cm. More preferably the prosthesis has a longitudinal length in therange of between 2 cm to 3 cm.

In a preferred embodiment of the prosthesis for use in repairing orresisting the formation of an inguinal hernia, the prosthesis is ofwidth or diameter in the range 0.5 cm to 7 cm. In a particularembodiment the prosthesis is of width or diameter in the range 1 cm to 4cm.

In a particularly preferred embodiment of the prosthesis for repairingor resisting the formation of an inguinal hernia, the prosthesis has atruncated conical shape wherein the outer surface of the prosthesis isformed by the conic surface.

A prosthesis of truncated conical shape in which a first end of theprosthesis has a diameter less than that of a second end has theadvantage that the prosthesis can be pushed first end into the defect,to plug the defect more easily.

In a particularly preferred embodiment, the prosthesis is of truncatedconical shape and further comprises a semi-circular channel extendingfrom a first end of the prosthesis to a second end of the prosthesis,the first end having a diameter less than the second end, wherein thesemi-circular channel is present in the conic outer surface of theprosthesis such that in cross-section a crescentic shaped prosthesis isprovided.

In an embodiment wherein the prosthesis has a truncated conical shape,the diameter of the widest end of the prosthesis, the second end, ispreferably in the range 1 cm to 7 cm and the diameter of the narrowestend, the first end, is preferably in the range 0.5 cm to 4 cm.

The channel receiving the anatomical structure can have any suitablecross sectional shape such as a semi-circular cross section. In anembodiment of the prosthesis for repairing or resisting the formation ofan inguinal hernia, the channel is sized in the range 0.5 cm to 3 cm inwidth and depth or where the channel of such an embodiment of theprosthesis is of circular or substantially circular cross section, forexample semi-circular cross section, the channel is in the range 0.5 cmto 3 cm in diameter.

In another embodiment of the prosthesis, the prosthesis is provided forrepairing or resisting the formation of a femoral hernia. In such anembodiment the length of the prosthesis is in the range 1 cm to 5 cm,the width of the prosthesis is in the range 0.5 cm to 7 cm and thechannel is sized to receive at least one of a femoral vein or otheranatomical structure.

In a preferred embodiment of a prosthesis provided for repairing orresisting the formation of a femoral hernia the prosthesis is oftruncated conical shape.

In an alternative embodiment the prosthesis provided for repairing orresisting the formation of femoral hernia is of triangular prism shape.In another embodiment, in cross section, the prosthesis is substantiallyarrowhead shaped having two outer accurate sides which extend from abase towards each other to form a point. Preferably the point isrounded. Alternatively, the prosthesis is substantially D shaped withthe accurate sides forming a more rounded arched point.

In a particular embodiment the prosthesis is formed from a number ofcomponent prosthetic parts which together form the complete prosthesisof the first aspect of the invention.

In an embodiment of the prosthesis formed from at least two componentparts, the parts may include means to attach the parts to each other toform the complete prosthesis.

It can be envisaged that the component prosthetic parts are of suitableshape such that in combination they provide a prosthesis which providesa channel able to receive an anatomical structure.

Typically the prosthesis is formed from resilient material such that theprosthesis can be flexed to open the access to the channel.

Suitably the prosthesis may be constructed of synthetic polymer whichmay be absorbable or non-absorbable, mesh material formed from syntheticpolymer, solid material, foam or hydrogel. Suitable synthetic polymersinclude, but are not limited to, polyester, polypropylene, PTFE,Mersilene, MPathy-Mesh™ and Mini-Mesh™ (available from MPathy MedicalDevices Limited, UK).

The prosthesis may be formed from rolls of mesh and/or comprises crossmembers to provide the prosthesis with strength to resist compression.The prosthesis may be formed from plastics material. In a particularembodiment the foam used to construct the prosthesis is polyurethane.

This is advantageous in that the channel may be formed such that, inuse, the prosthesis may be flexed from its rest position to an openposition to increase the width of the access to the channel enabling ananatomical structure to be more easily received by the channel. Theprosthesis may then be released to return to its rest position whereinthe anatomical structure is substantially enclosed by the channel whenthe prosthesis is located in the defect.

An anatomical structure may be partially received and enclosed by thechannel of the prosthesis. Typically an anatomical structure may bepartially received and enclosed by the channel such that at least 30% ofthe circumference of the anatomical structure is surrounded by theprosthesis.

The channel of the prosthesis is sized such that in use an anatomicalstructure may pass, when the prosthesis is in place in the body, withoutsubstantial compression of said anatomical structure by the prosthesis.Substantial compression of the anatomical structure is compression whichcauses pain to the patient or ischaemia of a distal organ. Preferablythe width of the anatomical structure, which in use passes through thechannel, is compressed less than 70%, even more preferably less than50%, yet more preferably less than 40%, even more preferably less than30%, even more preferably less than 20%, yet more preferably less than10%, even more preferably less than 5%, even more preferably less than3%, most preferably less than 1% by the channel of the prosthesis.

The level of compression experienced by the anatomical structure by theprosthesis when the anatomical structure passes through the channel ofthe prosthesis is preferably not more than venous pressure. Venouspressure is typically in the range 2 to 10 mm Hg.

In one embodiment of the prosthesis a single channel, sized to receiveat least one anatomical structure, is provided. In another embodimenttwo channels each sized to receive at least one anatomical structure,are provided. Each channel may be differently sized to receive at leastone anatomical structure in order to maximise the support provided bythe prosthesis while allowing the structure(s) to pass through the oneor more defined channels in the prosthesis.

A plurality of channels, each channel sized to receive one or moreanatomical structures, may be received by the prosthesis.

In a preferred embodiment of the present invention the prosthesisfurther comprises at least one flange provided on either one or bothends of the prosthesis. The provision of a flange on the prosthesis isadvantageous as it aids location of the prosthesis in the body and mayprovide additional support to tissue, muscle or an organ wallsurrounding the defect. In particular embodiments, the flange extendsfrom the prosthesis such that, in use, the flange provides aninferomedial extension to the prosthesis. For example, if a prosthesisof the invention further comprising a flange is used to plug an inguinalcanal, a first end of the prosthesis is positioned at the internalinguinal ring of the inguinal canal and a second end of the prosthesisis positioned at the external ring of the inguinal canal and a flangepresent on the second end of the prosthesis, can inferomedially extendfrom the prosthesis around the external ring.

The flange may be provided by a layer of synthetic mesh. Alternatively,the flange may be formed from a plurality of layers of synthetic mesh.

The layer(s) of mesh may overlap each other. Moreover, the layer(s) ofmesh may be of any desired shape to support the surrounding tissue,muscle or organ wall.

It is advantageous for the flange to be constructed of mesh. The meshhas minimal mass density in relation to its volume. In a preferredembodiment the flange is constructed of Mini-Mesh™.

A flange portion may contain structures or regions capable of receivingsutures or other fixing means to secure the flange around the anatomicalstructures received by the channel and/or to secure the flange to thesurrounding tissue. The flange may comprise more than one portion ofmaterial. For example, a flange may comprise two or more portions whichcan be arranged around an anatomical structure. The two portions mayattach to each other or overlap each other to form an extended region ofsupport to a hernia. The portions of the flange which overlap each othermay be formed of thinner material such that the overlapped region hasthe same thickness as the non-overlapped region of the flange.

In a particular embodiment of the prosthesis, the prosthesis has acrenated outer surface. The crenated outer surface allows the prosthesisto grip the tissues surrounding the prosthesis and aids retention of theprosthesis, in position, in the body.

In a second aspect of the present invention there is provided a kit ofparts including a prosthesis according to the first aspect of theinvention and synthetic mesh for overlaying the prosthesis when theprosthesis is positioned in the body. The kit may also includeinstructions as to the way in which the components of the kit are to beused.

According to a third aspect of the invention there is provided a methodfor treating a hernia comprising the steps:

-   -   exposing the hernia defect    -   providing a prosthesis wholly in the extra peritoneal        compartment of the abdominal wall to fill the defect but        providing a relatively pressure free passage of an anatomical        structure past the prosthesis.

The method is for treatment of abdominal hernia. Typically the methodmay be used for treatment of inguinal or femoral hernia.

The method may further include the step of fixing the prosthesis to themargins of the defect. One example of the way in which the prosthesismay be fixed to the margins of the defect is by suturing.

The method may further include the step of overlaying the prosthesiswith mesh.

The method preferably uses the prosthesis of the first aspect of theinvention or the kit of the second aspect of the invention.

Preferred features of each aspect of the invention are as for each ofthe other aspects mutatis mutandis unless the context demands otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be discussed, by way ofexample only, with reference to the accompanying figures in which;

FIG. 1 shows a perspective view of an embodiment of a prosthesis of theinvention from a second end;

FIG. 2 shows a perspective view of an embodiment of a prosthesis of theinvention from a first end;

FIG. 3 shows a perspective view of an embodiment of a prosthesis of theinvention in use;

FIG. 4 shows an embodiment of a prosthesis which further includes aflange provided at one end of the prosthesis;

FIG. 5 shows an indirect inguinal hernia;

FIG. 6 shows a hernia repaired using a conventional prosthesis of theprior art;

FIG. 7 shows an illustration of the anatomy around the inguinal canal;and

FIG. 8 shows an illustration of the anatomy around the femoral canal.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The invention is directed to an implantable prosthesis for repairing orresisting the formation of bodily hernia, in particular to plug or stopany aperture in the body in which a structure is required to passthrough or adjacent to the aperture. For example, the prosthesis may beused to plug the inguinal canal or the femoral canal. In theseembodiments, provided by way of example only, the prosthesis has achannel through which an anatomical structure, such as a spermatic cordor femoral vein, may pass without substantial compression of theanatomic structure.

As shown in FIGS. 1 and 2, in one embodiment, the prosthesis 10 is atruncated cone having a first end 14 and a second end 16, wherein thediameter of the first end is less than the diameter of the second end16, and an outer conic surface 15 extends between the ends. An innersurface 12 forming a channel is defined by a substantially scallopedportion removed from the outer surface of the truncated conicalprosthesis. It can be envisaged that the scalloped portion is formed bythe removal of a cylindrical portion which intersects the outer conicalsurface 15 to create a prosthesis of crescential cross-section. Theprosthesis resembles a wedge shape being narrower at the first end andwidest at its second end. An anatomical structure may pass through theprosthesis whilst being partially surrounded by the prosthesis tominimise the pressure or compression exerted on the anatomicalstructure.

It will be understood that the cross section of the channel may beformed by at least one straight edge such that the inner surface has astraight portion in cross section, for example a box section channel orat least one curved edge, to form a semi-circular channel or othershapes as should be apparent to one skilled in the art.

The channel 12 in the outer conical surface 15 of the prosthesis 10 issized to receive an anatomical structure(s) which passes through thedefect to be repaired or supported. As shown in the illustratedembodiment, FIG. 3, the channel formed by inner surface 12 receives ananatomical structure 30 such that the anatomical structure is partiallylocated in the channel. The channel minimising the compression of theanatomical structure against the edges of the defect when, in use, theprosthesis is located in the body.

In the embodiment of the prosthesis illustrated in FIGS. 1 to 3 for usein repair of an inguinal hernia the prosthesis is of truncated conicalshape with a semi-circular channel removed from the conical surface suchthat the prosthesis is substantially a wedge shape extending from afirst end 14 of minimal depth to a second end of diameter of around 19mm. The channel is of around 15 mm in depth at the second end, such thatin cross-section the second end is crescential in shape with a maximumdepth (x-y see FIG. 1) of 7 mm. The length of the prosthesis between thefirst and second ends is around 23 mm.

The portion removed from the truncated conical prosthesis to provide achannel can be in the range of 5 mm to 20 mm in width and depth.Although in the embodiment shown in FIGS. 1 to 3, the channel issubstantially semi-circular in cross section, the channel may be of anyshape. In addition, more than one channel may be present in theprosthesis, each channel being able to receive a particular anatomicalstructure.

Typically the prosthesis is in the range 1 cm to 5 cm in length betweenthe ends and around 1 cm to 4 cm in width and depth.

As shown in FIG. 3, in use, an anatomical structure 30 is received bythe channel 12, the channel indenting the conical surface of theprosthesis and linking the first and second ends 14 and 16, such thatthe anatomical structure can pass from one end of the prosthesis to theother without substantial compression. This differs from theconventional prosthesis 100, illustrated in FIG. 6, which lacks achannel. As illustrated in FIG. 6 when a conventional prosthesis is inuse to plug a defect, for example in abdominal wall muscle 36 and fat 34through which a hernia 32 of viscos 38 protrudes, an anatomicalstructure 30, such as a spermatic cord, is located between theprosthesis 100 and the edge of the defect. As the prosthesis 100 lacks achannel and the prosthesis is pushed into the defect, the anatomicalstructure is compressed.

The prosthesis and further the flange portion may be formed from a rangeof material including, but not limited to, polyester, polypropylene,PTFE, Mersilene, MPathy-Mesh™ or Mini-Mesh™ (available from MPathyMedical Devices Limited, UK).

The prosthesis may be formed using suitable construction techniques, forexample knitting and/or weaving of monofilament or multifilament yarns,moulding, ultrasonic, induction, vibration, infrared or laser welding.

As illustrated in FIG. 4, the prosthesis of the present invention mayfurther comprise a flange 18. The flange may extend laterally from atleast a first or second end or both ends of the prosthesis.

As shown in FIG. 4, when the prosthesis is located in the defect, theflange 18, which extends from the second end of the prosthesis, can aidthe positioning of the prosthesis, in the inguinal canal. Further, theflange may be formed from mesh and extend from the prosthesis such thatwhen the prosthesis is implanted in the body the mesh extends to themusculature surrounding the inguinal canal and provides support thereto.In particular embodiments, the flange can extend from the prosthesisinferomedialy, which aids the use of the prosthesis in the treatment ofdirect inguinal hernia.

The flange may include more than one layer of mesh and said layers mayoverlap each other. Moreover, the flange may include cut out potions toallow it to be placed around or over protruding structures or attachmentmeans to attach the flange to itself and/or tissue, muscle etc. Suchattachment means include sutures or other fixing means.

In embodiments wherein a flange is provided on both ends of theprosthesis, the flange, when the prosthesis is in use, may be providedaround the internal ring and external ring of the inguinal canal suchthat the tissue and fascia around the inguinal ring is sandwichedbetween at least two layers of mesh. The flange thus supports the tissueand/or fascia and minimises the likelihood of organs or structuresrupturing or protruding through the tissue and/or fascia.

An embodiment of the prosthesis of the first aspect of the invention canbe utilised to repair or resist the formation of an inguinal canal.

As illustrated in FIGS. 7 and 8 the sac of an indirect inguinal hernia40 may extend from the external ring 42 of the inguinal canal 44. Theinguinal canal extending between the external ring 42 and an internalring 46.

In use, a prosthesis is inserted into the inguinal canal such that afirst end of the prosthesis is positioned at the internal inguinal ring46 and the second end is positioned at the external ring 42 of theinguinal canal. When located in the inguinal canal 44 the prosthesisacts to minimise the protrusion of organs or the other body partsthrough the inguinal canal, but as the prosthesis includes a channel,there is provided a passage for selected anatomical structures, such asthe spermatic cord, to pass through the prosthesis without beingsubstantially compressed by the prosthesis or between the prosthesis andthe surrounding tissue.

To aid the fixation of the prosthesis in the inguinal canal theprosthesis may be crenated on its outer surface. Such crenations willproject from the outer surface of the prosthesis into the surroundingtissue and minimise the movement of the prosthesis once it has beensuitably positioned.

An embodiment of the prosthesis of the invention may be used to repairor resist the formation of a femoral hernia. As illustrated in FIGS. 7and 8 the femoral canal 48 lies between the fascia transversalis 50 andfascia iliaca 52 with the femoral vein 54, femoral artery 56 and femoralnerve 58 being present to one side of the femoral canal. As shown inFIG. 7, a sac of a femoral hernia 60 may extend along and pass out ofthe femoral canal.

In use, an embodiment of the prosthesis for treatment of femoral herniamay be inserted into the femoral canal to minimise the protrusion of thehernia sac through the femoral canal. During insertion of the prosthesisinto the femoral canal, the channel of the prosthesis is orientated suchthat expansion of the femoral vein is into the channel of theprosthesis. Thus, in contrast to conventional prosthesis, thecompression of the expanded vein against the prosthesis and/or thesurrounding tissue will be minimised. In addition, the channel willstill provide for movement in the lymphatic system from a lower limb toexternal iliac nodes.

In one embodiment, a prosthesis of the present invention, for use inplugging the femoral canal, is substantially of triangular prism shapein cross section such that it is shaped to fit into the femoral canal.In another embodiment, in cross section, the prosthesis is substantiallyarrowhead shaped having two outer accurate sides which extend from abase towards each other to form a point. Preferably the point isrounded. Alternatively, the prosthesis is substantially D shaped withthe accurate sides forming a more rounded arched point. In eachembodiment a channel is provided in the outer surface of the prosthesisto receive the femoral vein when it is expanded. When the prosthesis issubstantially arrowhead or D shaped, it is preferred that the baseportion is indented towards the point to receive an anatomicalstructure.

The prosthesis is sized such that it can be suitably located into thefemoral canal. In particular embodiments the prosthesis is sized suchthat it is of length in the range 1 cm to 5 cm, of width at a first endfor insertion into the femoral canal in the range 0.5 cm to 3 cm and asecond end at 0.5 cm to 5 cm.

The channel need only be an indentation in the outer surface of theprosthesis to receive the femoral vein when expanded such that thepressure exerted on the vein, during expansion of the vein, by theprosthesis is minimised.

As discussed above, a prosthesis for use in treating femoral hernia mayfurther include a flange at either or both ends of the prosthesis,wherein the flange extends around the femoral canal and thus supportsthe surrounding tissue or fascia. As previously discussed such a flangemay also contain cutouts to accommodate structures such as the femoralnerve and/or artery.

The prosthesis of the present application has been designed to take intoconsideration the anatomical structures and properties of the inguinaland femoral canal to minimise the disruption of these structuresfollowing location of the prosthesis.

Various modifications can be made without departing from the scope ofthe invention, for example, flanges extending from the faces of theprosthesis, as discussed above, may be formed from material with memory,such that following placement in the body the flanges move from acollapsed position to an extended position to secure the prosthesis inthe body.

1. A prosthesis for repair or to resist the formation of an abdominalwall hernia comprising at least an outer surface and an inner surfacewherein the inner surface forms at least one channel which, in use,partially receives and encloses an anatomical structure such that atleast 30% of the circumference of the anatomical structure is surroundedby the prosthesis and the an anatomical structure may pass through theprosthesis when the prosthesis is in place in the body withoutsubstantial compression of said anatomical structure.
 2. The prosthesisas claimed in claim 1 of width in the range 0.5 cm to 7 cm.
 3. Theprosthesis as claimed in claim 1 of longitudinal length in the range 1to 5 cm.
 4. The prosthesis as claimed in claim 1 wherein the channel isof dimensions in the range 0.5 cm to 3 cm in width and depth.
 5. Theprosthesis as claimed in claim 1 wherein the inner surface defines ascalloped channel.
 6. The prosthesis as claimed in claim 1 wherein thechannel of the prosthesis is sized such that in use an anatomicalstructure may pass, when the prosthesis is in place in the body, thewidth of the anatomical structure being compressed less than 70%.
 7. Theprosthesis as claimed in claim 1 wherein the prosthesis has a truncatedconical shape.
 8. The prosthesis as claimed in claim 7 wherein thediameter of the truncated conical shaped prosthesis at the widest end ofthe prosthesis is in the range 0.5 cm to 7 cm and the diameter of thenarrowest end is in the range 0.5 cm to 4 cm.
 9. The prosthesis asclaimed in claim 1 wherein the prosthesis further comprises at least oneflange which extends from the prosthesis.
 10. The prosthesis as claimedin claim 9 wherein the flange is a portion of synthetic mesh.
 11. Use ofa prosthesis as claimed in claim 1 to repair or to resist the formationof an abdominal hernia.
 12. Use of a prosthesis as claimed in claim 1 torepair or to resist the formation of an inguinal hernia, the channelbeing sized to receive a spermatic cord without substantial compressionof the spermatic cord.
 13. Use of a prosthesis as claimed in claim 1 torepair or to resist the formation of femoral hernia the channel beingsized to receive a femoral vein.
 14. A kit including a prosthesisaccording to claim 1 and synthetic mesh to overlay the prosthesis.
 15. Amethod for treating hernia comprising the steps: exposing the herniadefect providing a prosthesis wholly in the extra peritoneal compartmentof the abdominal wall to fill the defect but which provides a relativelypressure free passage of an anatomical structure past the prosthesis.16. The method of claim 15 wherein the method is for treatment ofinguinal or femoral hernia.
 17. The method of claim 15 wherein theprosthesis provided to fill the defect is the prosthesis of claim 1.